Method and apparatus for creating an annular seal in a wellbore

ABSTRACT

A workstring apparatus for creating an annular seal in a wellbore is described. Workstring comprises at least one packer apparatus comprising a body portion and an elastomeric packer element which is deformable into an outwardly deployed condition to deform wellbore casing. A fluid accumulator is provided to hold fluid to actuate at least one hydraulic cylinder of the packer apparatus. An electrically powered pump is operable to pump fluid from accumulator into the hydraulic cylinders of packer apparatus to deform the elastomeric packer element outwardly. A wireline connects the workstring to the surface and provides electrical power to the workstring. Wireline may be an electrical feed such as a composite rod or e-coil.

The present invention relates to a method of creating an annular seal in the annulus between a wellbore and a casing disposed in the wellbore, wherein at least one tubular casing element comprising an external sealing element disposed thereon is disposed in the wellbore. The present invention also relates to a workstring apparatus for creating an annular seal in the annulus between a wellbore and a casing disposed in the wellbore. The present invention also relates to a method of placing a casing patch in a wellbore, a method of completing a wellbore and a tubular casing element for a wellbore.

In hydrocarbon wellbores, sustained annular pressure is defined as unwanted fluid pressure in the annulus between the wellbore casing and the wellbore. This pressure can migrate towards the surface and can therefore pose a risk to wellbore integrity.

To prevent pressure migration, it is desirable to create seals in the annulus between the wellbore casing and the wellbore. However, since the annulus is generally full of cement, the creation of such annular seals can be problematic. Known methods of creating such seals include relatively costly expandable metal barrier products, open hole packers and swellable packers.

Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.

According to an aspect of the present disclosure, there is provided a method of creating an annular seal in the annulus between a wellbore and a casing disposed in the wellbore, wherein at least one tubular casing element is disposed in a wellbore, said tubular casing element comprising an external sealing element disposed thereon, the method comprising:

locating a workstring in the wellbore, the workstring comprising:

at least one packer apparatus comprising a body portion, an elastomeric packer element disposed on said body portion and at least one hydraulic cylinder, wherein said elastomeric packer element is configured to be deformed into an outwardly deployed condition in response to actuation of said at least one hydraulic cylinder to deform casing located in the wellbore;

a fluid accumulator arranged to hold fluid for actuation said at least one hydraulic cylinder;

an electrically powered pump arranged to pump fluid from said fluid accumulator to actuate said at least one hydraulic cylinder; and

a wireline arranged to supply electrical power to said electrically powered pump and hold said workstring at a desired position in a wellbore;

moving the workstring to a position at which said elastomeric packer element is located at the same depth as said external sealing element;

operating said electrically powered pump to actuate said at least one hydraulic cylinder to deform said elastomeric packer element outwardly to contact and deform said tubular casing element outwardly and compress said external sealing element against the surface of a wellbore or casing in which said tubular casing element is located to form an annular seal.

This provides the advantage of a low cost and reliable method of creating an annular seal in a wellbore between casing and the surface of the wellbore or between two concentric casing elements. The workstring can be moved along the wellbore to a position at which an external sealing element is located on the tubular casing and actuated to deform the casing outwardly, compressing the external sealing element against the wellbore and therefore providing a reliable seal. This can be done multiple times along the casing to provide multiple annular seals and therefore multiple zones of isolation.

This therefore provides a reliable and relatively inexpensive means of preventing annular pressure migration towards the surface.

In a preferred embodiment, a plurality of tubular casing elements having external sealing elements disposed thereon are disposed in a wellbore, and wherein said workstring comprises a plurality of packer apparatuses each having an elastomeric packer element, the method further comprising:

moving the workstring to a position in the wellbore at which said elastomeric packer elements are located at the same depths as said external sealing elements; and

operating said electrically powered pump to actuate said plurality of packer apparatuses to deform the respective plurality of elastomeric packer elements outwardly to contact and deform a plurality of tubular casing elements outwardly and compress said plurality of external sealing elements against the surface of a wellbore or casing in which said tubular casing element is located to form a plurality of annular seals.

This provides the advantage that a plurality of annular seals can be created in a single run of the workstring to produce multiple zones of isolation.

In a preferred embodiment, the workstring further comprises sensor apparatus configured to sense characteristics of the formation of the portion of wellbore in which the workstring is located and/or to locate the position of external sealing elements of tubular casing elements disposed in the wellbore, the method further comprising:

moving the workstring through the wellbore to a position at which the sensor apparatus indicates to an operator of the workstring that an annular seal is desirable at that location in the wellbore and/or an external sealing element is located adjacent said at least one elastomeric packer element; and

operating said electrically powered pump to deform. said elastomeric packer element outwardly to contact and deform said tubular casing element outwardly and compress said external sealing element against the surface of a wellbore or casing in which said tubular casing element is located to form an annular seal.

This provides the advantage of a reliable means to quickly locate the external sealing elements to reduce the time taken to create annular seals to therefore improve the efficiency of the sealing operation.

In a preferred embodiment, the step of moving the workstring through the wellbore to a position at which the sensor apparatus indicates to an operator of the workstring that an annular seal is desirable at that location in the wellbore and/or an external sealing element is located adjacent said at least one elastomeric packer element includes operating fibre optic cables to sense wellbore parameters to indicate characteristics of the casing and/or fluid migration in the wellbore to the operator.

This provides the advantage that by using fibre optics along the wireline or composite rod. to measure changes downhole, data can be gathered in real time indicating wellbore and casing parameters over several kilometres. This provides a very effective sensor along the wireline to measure parameters such as strain changes, pressure, temperature and fluid flow to both determine how effective the annular seal created is as well as accurately locate portions of the wellbore for sealing.

Said at least one packer apparatus may comprise locking means configured to retain said elastomeric packer element in the outwardly deployed condition, said at least one packer apparatus further comprising a detachable portion containing said elastomeric packer element, the method further comprising:

after said at least one packer apparatus has been operated to form an annular seal in the wellbore, detaching said detachable portion of said at least one packer apparatus of which the locking means has retained the elastomeric packer element in the outwardly deployed condition to deform casing to leave said detachable portion in the wellbore to act as a bridge plug.

This provides the advantage of a means to create a bridge plug in a wellbore in a straightforward manner after the sealing operation is complete.

The method may further comprise pumping cement into the wellbore to sit on top of said detachable portion.

The method may further comprise:

lining a wellbore with a plurality of tubular casing elements;

pumping cement into the annulus between said plurality of tubular casing elements and the surface of the wellbore or casing in which said plurality of casing elements is located; and

locating said work string in the wellbore and operating said work string to form at least one annular seal in said wellbore before said cement has set.

This provides the advantage of a method of creating annular seals in a wellbore disposed between sections of cemented casing. This therefore provides the advantage of significantly improving wellbore integrity.

This also provides the advantage of enabling completion of a wellbore in a manner which provide pre-isolated production zones to simplify hydrocarbon production from multiple zones.

According to another aspect of the present disclosure, there is provided a workstring apparatus for creating an annular seal in the annulus between a wellbore and a casing disposed in the wellbore, the workstring comprising:

-   -   at least one packer apparatus comprising:     -   a first body portion removably connectable to a second body         portion;     -   an elastomeric packer element disposed on said first body         portion, said elastomeric packer element configured to be         deformed into an outwardly deployed condition in response to         actuation of at least one piston disposed on said second body         portion;     -   locking means disposed on said first body portion to retain said         elastomeric packer element in the outwardly deployed condition;     -   wherein said first body portion can be disconnected from said         second body portion after said elastomeric packer element is         moved to the outwardly deployed condition to deform casing in a         wellbore in which the assembly is disposed to enable retrieval         of said second body portion from said wellbore;

a fluid accumulator arranged to hold fluid for actuation said at least one hydraulic cylinder;

an electrically powered. pump arranged to pump fluid from said fluid accumulator to actuate said at least one hydraulic cylinder; and

a wireline arranged to supply electrical power to said electrically powered pump and hold said workstring at a desired position in a wellbore; wherein

operating said electrically powered pump to actuate said at least one hydraulic cylinder deforms said elastomeric packer element outwardly to contact and deform a tubular casing element in which said packer apparatus is located outwardly to form an annular seal.

This provides the advantage of an apparatus for creating annular seals in wellbores that can be used reliably at any depth without having to overcome the problems of pumping fluid from the surface to actuate hydraulic elements of the workstring. This means that the workstring can be reliably and repeatedly used to create multiple annular seals in a single run in a wellbore.

By providing a fluid accumulator and electrically powered pump, this provides the advantage of preventing contamination of the apparatus with wellbore fluid.

This also provides the advantage that part of the packer apparatus can be left in the wellbore with the elastomeric packer element deployed outwardly to prevent elastic deformation of the deformed wellbore casing which can result in seal failure.

Furthermore, this provides the advantage that the relatively costly hydraulic section of the tool can be retrieved to the surface for reuse.

Moreover, this provides the additional advantage that part of the assembly left in the wellbore can be used as a bridge plug.

In a preferred embodiment, the apparatus further comprises sensor apparatus configured to sense characteristics of the formation of the portion of wellbore in which the workstring is located and/or to locate the position of an external sealing element of tubular casing elements disposed in the wellbore.

This provides the advantage of enabling accurate location at any depth of a position along the wellbore at which an annular seal is to be created.

In a preferred embodiment, said sensor apparatus comprises at least one fibre optic cable and control apparatus configured to sense characteristics of the formation of the portion of wellbore in which the workstring is located and/or to locate the position of an external sealing element of tubular casing elements disposed in the wellbore based on light signals from said at least one fibre optic cable.

This provides the advantage that by using fibre optics along the wireline or composite rod to measure changes downhole, data can be gathered in real time indicating wellbore and casing parameters over several kilometres. This provides a very effective sensor along the wireline to measure parameters such as strain changes, pressure, temperature and fluid flow to both determine how effective the annular seal created is as well as accurately locate portions of the wellbore for sealing.

In a preferred embodiment, said locking means comprises:

a first plurality of teeth disposed on an outer surface of said first body portion; and

a ratchet member having a second plurality of teeth disposed thereon for engagement with said first plurality of teeth;

wherein said ratchet member is able to move in a first direction along said first body portion during deformation of said elastomeric packer element but is prevent from movement in a second direction, opposite to said first direction by engagement of said first and second pluralities of teeth.

Said ratchet member may comprise a split ring.

Said locking means may further comprise a ratchet retainer ring in engagement with said elastomeric packer element.

In a preferred embodiment, the apparatus further comprises an electrically operated release apparatus to enable disconnection of the first body portion from the second body portion.

This provides the advantage of a means of enabling the first and second body portions to be disconnected to facilitate retrieval of the hydraulic section to the surface for reuse and enabling the packer element to remain downhole to ensure casing deformation and therefore seal integrity.

In a preferred embodiment, the apparatus further comprises a floating piston in fluid communication with both:

-   -   fluid held in the fluid accumulator; and     -   fluid located in a wellbore in use;

such that fluid held in the fluid accumulator is isolated from fluid located in the wellbore but is at an equal pressure to fluid located in the wellbore.

This provides the advantage of ensuring that the apparatus is able to operate at any wellbore pressure. Since the internal pressure in the hydraulic section of the apparatus is equalised with wellbore pressure, this means that the electrical pump does not have to operate to overcome the pressure of the column of fluid above which the apparatus is located.

In a preferred embodiment, the apparatus further comprises a a plurality of packer apparatuses.

According to a further aspect of the present disclosure, there is provided a method of placing a casing patch in a wellbore, the method comprising:

mounting a tubular casing element having an external sealing element disposed thereon on a workstring according as defined above;

moving said work string to a location in the wellbore at which a casing patch is required;

operating said work string to deform said tubular casing element to form an annular seal at the desired location of said casing patch and disconnect said tubular casing element from the work string; and

moving the work string away from said tubular casing element forming said casing patch.

This provides the advantage of enabling casing that has been perforated for use in fracking or casing that has been breached to be patched. This means that operators can create sealed production compartments using the workstring apparatus and then perforate sections of the casing to allow the compartment to produce oil or gas or steam with geothermal wells. Later in the life of the well when it is desired to seal off such production compartments, a casing patch can then be placed at the desired position in the wellbore in a relatively low cost and reliable manner.

According to another aspect of the present disclosure, there is provided a method of completing a wellbore, the method comprising:

lining a wellbore with at least one tubular casing element, said at least one tubular casing element comprising an external sealing element disposed thereon; and

creating an annular seal between a wellbore and a casing disposed in the wellbore as defined above.

This provides the advantage of a low cost and reliable method of creating an annular seal in a wellbore between casing and the surface of the wellbore or between two concentric casing elements. The workstring can be moved along the wellbore to a position at which an external sealing element is located on the tubular casing and actuated to deform the casing outwardly, compressing the external sealing element against the wellbore and therefore providing a reliable seal. This can be done multiple times along the casing to provide multiple annular seals and therefore multiple zones of isolation.

This therefore provides a reliable and relatively inexpensive means of preventing annular pressure migration towards the surface.

According to a yet further aspect of the present disclosure, there is provided a tubular casing element for a wellbore, the tubular casing element comprising an external sealing element disposed thereon, wherein the external sealing element is a tubular sleeve formed from two or more of the following materials:

-   -   an elastomer;     -   a composite material;     -   an alloy;     -   a metal; or     -   Teflon ®.

This provides the advantage of a tubular casing element that can be used to create annular seals in a wellbore that can also be adapted to be used in any particular wellbore conditions.

Preferred embodiments of the present invention will now be described, by way of example only and not in any limitative sense, with. reference to the accompanying drawings in which:

FIG. 1 is an elevation view of a bottom hole assembly (BHA) comprising a workstring apparatus in accordance with the first embodiment of the present invention for creating an annular seal in the annulus between a wellbore and a casing disposed in a wellbore;

FIG. 2 a is a side view of a packer apparatus of the workstring of FIG. 1 ;

FIG. 2 b is a cross-sectional view of the packer apparatus of FIG. 2 a showing the elastomeric packer element in the retracted condition;

FIG. 3 a is a side view of the fluid accumulator of the workstring of FIG. 1 ;

FIG. 3 b is a cross-sectional view of the fluid accumulator of FIG. 3 a;

FIG. 4 is an elevation view of a tubular casing element comprising an. external sealing element in accordance with a second embodiment of the invention;

FIG. 5 is an elevation view of the external sealing element of the tubular casing element of FIG. 4 ;

FIG. 6 is a cross-sectional view of the tubular casing element of FIG. 4 ;

FIG. 7 a is an elevation view of the workstring of FIG. 1 disposed in casing in a wellbore in a first stage of an operation to create annular seals in the wellbore;

FIG. 7 b is a view corresponding to FIG. 7 a showing the workstring deforming casing to form annular seals;

Figure 8 a is an elevation view of the workstring of FIG. 1 in casing disposed in a wellbore in a first stage of a surface casing vent flow remediation operation;

FIG. 8 b is a view corresponding to FIG. 8 a in a second stage of a surface casing vent flow remediation operation;

FIG. 9 a is an elevation view of the workstring of FIG. 1 in a first stage of an operation to place a casing patch in a wellbore;

FIG. 9 b is a view corresponding to FIG. 9 a showing the workstring in position in a wellbore casing;

FIG. 9 c is a view corresponding to FIG. 9 b showing the packer apparatuses actuated to create a casing patch;

FIG. 10 a is a longitudinal cross-sectional view of an embodiment of a packer apparatus for use in the workstring of FIG. 1 ;

FIG. 10 b is a longitudinal cross-sectional view of the packer apparatus of FIG. 10 a in the condition in which fluid is pumped into the hydraulic cylinders by the electrically operated pump to deploy the elastomeric packer element to deform casing and actuate the locking means;

FIG. 10 c is a longitudinal cross-sectional view of the packer apparatus of FIGS. 10 a and lOb in the separated condition; and

FIG. 11 is a close-up detail of box A of FIG 10 b showing the locking means of the packer apparatus.

Referring to FIGS. 1 to 3 b, a workstring apparatus 2 for creating an annular seal in a wellbore comprises at least one packer apparatus 4 comprising a body portion 6 and an elastomeric packer element 8 which is deformable into an outwardly deployed condition to deform wellbore casing. A fluid accumulator 10 is provided to hold fluid to actuate at least one hydraulic cylinder 12 of the packer apparatus 4.

An electrically powered pump 14 is operable to pump fluid from accumulator 10 into the hydraulic cylinders 12 of packer apparatus 4 to deform the elastomeric packer element 8 outwardly. A wireline 16 connects the workstring 2 to the surface and provides electrical power to the workstring 2. Wireline 16 may be an electrical feed such as a composite rod or e-coil.

The workstring 2 also comprises sensor apparatus 18 which may include a casing collar locator 20 and formation evaluation logging tools 22. The sensor apparatus enables the workstring 2 to sense characteristics of the formation of the portion of the wellbore in which the workstring is located and also enables location of the position of an external sealing element of tubular casing elements disposed in the wellbore. The sensor apparatus 18 therefore allows for real time data acquisition to give the workstring operator real time control of what is happening downhole at the location of the bottom hole assembly (BHA).

The sensor apparatus may also include a fibre optic cable assembly 19 on wireline 16 and control apparatus (not shown) to analyse light signals in the fibre optics to provide data on wellbore conditions such as strain changes, pressure, temperature and fluid flow. This enables operators to determine how effective seals created by the workstring 2 are.

The wireline 16 or COROD (Continuous Rod) may contain the ability to take fibre optic measurements in both the static and dynamic regimes for formation evaluation and fluid migration. Single or multiple fibre optic cable assemblies with the option of single or multi-electrical conductors can be contained inside either electric line, braided cable or continuous rod. Such fibre optic and electrical measurements may measure distributive temperature, acoustics, strain, fluid migration and formation characteristics. The cable and logging tools provide the ability to monitor a change in fluid migration real time downhole with accurate depth measurements.

The cable and/or logging tools show the movement of fluid migration behind the casing prior to activation of the packer apparatus 4. During packer apparatus activation continual measurements can be taken through the cable and logging tools to show a real time change downhole on the casing and fluid migration. These measurements show the ability to shut off fluid migration real time downhole and further confirm changes in the casing expansion during and after the apparatus activation. The cable and logging tools also have the ability to show change post activation with movement of the logging tools and cable above and below the area of the casing in which a seal has been created. The logging tools and cable can also be used to show changes in trapped gas up hole as the workstring is moved through the wellbore.

Workstring apparatus 2 further comprises a cable head 20 which connects the wireline 16 to the bottom hole assembly. Cable head 20 is able to signal along wireline 16 if the workstring apparatus 2 becomes stuck. Release tool 22 can then be activated to release the wireline from. the rest of the apparatus 2 to enable retrieval. An emergency release solenoid valve ensures that if power loss occurs the workstring apparatus 2 will be in the undeployed condition for easy retrieval with a fishing tool.

Casing collar locator 20 may be replaced with a gamma ray tool for precise depth correlation. Formation evaluation logging tools 22 enable the operator to determine physical properties of the well such as formation density, porosity, permeability, type and natural fracture orientation.

Referring to FIGS. 2 a and 2 b , packer apparatus 4 comprises a body portion 6 formed from several lengths of tubing defining the outer surfaces of hydraulic cylinders 12. Hydraulic cylinders 12 are formed between inner mandrel sections 24 each having an internal port 26 providing fluid communication between the inside of mandrel 24 and hydraulic cylinder 12. Annular ports 28 are provided through tubular portions defining the body portion 6 to enable wellbore fluid to be exhausted. The hydraulic cylinders 12 therefore form multiple pistons to drive ring 30 to deform elastomeric packer element 8 when fluid pressure is increased in hydraulic cylinders 12 above annular pressure. The modular configuration of the hydraulic cylinders 12 enable the number of cylinders to be changed to increase and decrease the force available to the operator.

Referring to FIGS. 10 a to 10 d and 11, packer apparatus 104 may preferably be used in workstring 2 instead. of packer apparatus 4. Packer apparatus 104 for deforming casing 50 comprises a first body portion 106 a removably connectable to a second body portion 106 b. An elastomeric packer element 108 is disposed on the first body portion 106 a. and is configured to be deformed into an outwardly deployed condition (FIGS. 10 b and 10 c ) in response to actuation of at least one hydraulic cylinder 112 disposed on the second body portion 106 b.

A locking means 170 is disposed on the first body portion 106 a and is configured to retain the elastomeric packer element 108 in the outwardly deployed condition after it has deformed casing 50. The first body portion 106 a can be disconnected from the second body portion 106 b after the elastomeric packer element is deployed to deform casing 50 to enable retrieval of the second body portion 106 b from the wellbore.

In. the fully assembled condition as shown in FIG. 10 a , the packer apparatus defines a longitudinal bore 105 which passes through both the first and second body portions 106 a and 106 b. When separated as shown in FIG. 10 c , the longitudinal bore comprises a first part 105 a and a second part 105 b. Hydraulic cylinders 112 are in fluid communication with the longitudinal bore 105 via internal ports 126. Annular ports 128 is provided to enable wellbore fluid to be exhausted during actuation of the hydraulic cylinders 112. it can be seen that a plurality of hydraulic cylinders 112 (three in the embodiment shown) are mounted in a stacked configuration using inner mandrel sections 124 in series on the second body portion 106 b.

Increasing the number of hydraulic cylinders 112 increases the area available on which pressurised fluid pumped into longitudinal bore 105 from the accumulator 10 (FIGS. 3 a and 3 b ) can act to increase the force available to drive the deformed. elastomeric packer element 108 into casing 50 to cause deformation.

Locking means 170 comprises a ratchet member 172 in the form of a split ring which is held in place on the first body portion 106 a by a retainer ring 174 and an axial retainer 176. A first plurality of teeth 178 is formed on the surface of the first body portion 106 a and a second plurality of teeth 180 is formed on the internal surface of ratchet member 172. The configuration of the respective sets of teeth 178 and 180 enable the ratchet member 172 to skip over teeth 178 as it moves in the direction of compression of elastomeric packer element 108 (to the right in the drawings which corresponds to the downhole direction). However, the configuration of teeth 178 and 180 prevent the ratchet member 172 moving in the opposite direction (to the left in the drawings) such that once deployed, the elastomeric packer element 108 is held in the deformed condition.

The first body portion 106 a and second body portion 106 b can be disconnected from one another. Collar portion 190 forms part of an electrically operated release apparatus that is actuated by a signal down wireline 16. When the elastomeric packer element 108 is deployed to deform casing 50 and create annular seal 60 as shown in FIG. 10 c , the elastomeric packer element 108 grips he casing. The release mechanism can the be operated to enable separation and retrieval of the second body portion 106 b and the hydraulic section formed from hydraulic cylinders 112 to the surface for reuse. For example, shear pins (not shown) could be used to releasably connect first and second body portions 106 a and 106 b . First body portion 106 a remains downhole in deformed casing 50 to prevent elastic deformation of the seal 60 to prevent seal failure.

Referring to FIGS. 3 a and 3 b , accumulator 10 comprises a floating piston 32 defining an internal side 34 filled with hydraulic fluid used to pressurise hydraulic cylinders 12 of the packer apparatus 4. Internal chamber 34 is therefore isolated from the annular wellbore pressure. Wellbore fluid can enter the accumulator 10 through ports 36 after passing through filter 38 to avoid debris entering the annular pressurised side 40 of the floating piston 32. As a consequence, wellbore pressure entering the annular pressure side 40 of the accumulator 10 moves floating piston 32 to pressurise internal hydraulic fluid in the internal side 34 of the accumulator 10 which is in fluid communication via a valve system with packer apparatus 4. This ensures that the packer apparatus 4 is equalised with the annular pressure in the wellbore until such time as electric pump 14 is operated to increase pressure the hydraulic chambers 12 to deploy the packer apparatus.

Referring to FIGS. 4 to 6 , a tubular casing element 50 is a standard length of casing having a casing collar 52 with an external thread to receive the external thread 54 of an adjacent length of casing. As will be familiar to persons skilled in the art, tubular casing elements 50 are generally formed from metal such as steel. A casing centraliser 56 is located adjacent casing collar 52. Tubular casing element 50 comprises an external sealing element 58 which could be a rubber packing glove or preferably be formed from two or more materials such as an elastomer, an alloy, aluminium or Teflon®. This enables the external sealing element 58 to be chosen with the correct properties to seal in a particular formation.

Referring to FIGS. 7 a and 7 b , a method of creating an annular seal in the annulus between a wellbore and a casing disposed in the wellbore according to an embodiment of the present invention will now be described.

Workstring 2 is located at a position in wellbore 100 at which one or more annular seals are to be formed. The wellbore 100 has previously been lined with tubular casing elements 50. No cementing is required. The workstring 2 can be deployed via a pump down deployment method or a tractor method for example in horizontal wells. The casing collar locator 20, fibre optics 19 and/ or gamma ray tool is able to sense the location of casing collars or other characteristics of the wellbore indicating that the packer apparatuses 4 are located adjacent tubular sealing elements 58. When workstring 2 is at the desired location as shown in FIG. 7 a , a signal is sent down the wireline (not shown) to position a control valve in the expansion position which pumps fluid from the accumulator into the hydraulic cylinders of the packer apparatus 4. This deforms the elastomeric packer elements 8 outwardly to contact casing 50. The force generated is sufficient to plastically deform the casing 50 and form annular seals 60 as external sealing elements 58 are compressed against the surface of wellbore 100. This creates an isolated section 102 of the wellbore 100.

The method of FIGS. 7 a and 7 b can also be conducted after the annulus between the wellbore 100 and casing 50 has been cemented, but before the cement has set. It can also be seen that two packer apparatuses 4 are used to create two annular seals 60. However, a larger or smaller number of packer apparatuses 4 can be used or connected to the accumulator depending on the particular conditions of the wellbore. The workstring 2 can then be positioned on a different portion of the wellbore to repeat the operation.

It should be understood that the method described in connection with FIGS. 7 a and 7 b (as well, as any method for creating annular wellbore seals disclosed herein) could use the packer apparatus 104 of FIGS. 10 a, 10 b, 10 c and 11 rather than packer apparatus 4 to create annular seals. Use of packer apparatus 104 enables the elastomeric packer element 108 to remain downhole to prevent elastic deformation of casing 50 which can cause seal failure. First part 106 a of packer 104 left downhole also provides a bridge plug and a base for cement.

Referring to FIGS. 8 a and 8 b , in a further embodiment, wellbore 200 is lined with cemented tubular casing elements 50. In some wellbores, micro-annuli may be created if the cement has not bonded correctly. This may be caused by poor cement quality, fluid or debris not allowing proper bonding of the cement to the casing, pressure changes, cement dehydration, temperature changes or contraction of the cement formation or casing. When decommissioning a well, such casing vent flows must be shut off at the source. Current industry practice is to perforate the casing 50 and squeeze cement to try to shut off the vent.

However, it has been found that workstring 2 can be used to shut off such micro-annuli. For example, the workstring 2 is positioned at a location at which micro-annuli are sensed and packer apparatus 4 is actuated by pumping fluid from the accumulator to deform tubular casing element 8 and deform casing 50 outwardly to form an annular seal 60 closing off the vents.

Referring to FIGS. 9 a to 9 c , a method of deploying a casing patch of a third embodiment of the invention will be described.

Referring to FIG. 9 a , a casing patch 70 is mounted to workstring 2 at the surface. Referring to FIG. 9 b , workstring 2 to which casing patch 70 has been mounted is then deployed to the desired location in the wellbore. Referring to FIG. 9 c , packer apparatuses 4 are then operated to deploy elastomeric packer elements 8 and deform the casing patch 70 against casing 50 located in the wellbore to patch out the casing. This also de-latches the casing patch 70 from the workstring 2.

Multiple casing patches can be run at one time. In order to do this the workstring 2 is outfitted with multiple casing patch sections and control valving is set to pump one section at a time. The patch nearest the bottom will be deployed first followed by the patch above.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. In particular, the above embodiments have been described with reference to creating seals between casing and a wellbore. The same methods can be used to create seals between concentric sections of casing. 

1. A method of creating an annular seal in the annulus between a wellbore and a casing disposed in the wellbore, wherein at least one tubular casing element is disposed in a wellbore, said tubular casing element comprising an external sealing element disposed thereon, the method comprising: locating a workstring in the wellbore, the workstring comprising: at least one packer apparatus comprising a body portion, an elastomeric packer element disposed on said body portion and at least one hydraulic cylinder, wherein said elastomeric packer element is configured to be deformed into an outwardly deployed condition in response to actuation of said at least one hydraulic cylinder to deform casing located in the wellbore; a fluid accumulator arranged to hold fluid for actuation said at least one hydraulic cylinder; an electrically powered pump arranged to pump fluid from said fluid accumulator to actuate said at least one hydraulic cylinder; and a wireline arranged to supply electrical power to said electrically powered pump and hold said workstring at a desired position in a wellbore; moving the workstring to a position at which said elastomeric packer element is located at the same depth as said external sealing element; operating said electrically powered pump to actuate said at least one hydraulic cylinder to deform said elastomeric packer element outwardly to contact and deform said tubular casing element outwardly and compress said external sealing element against the surface of a wellbore or casing in which said tubular casing element is located to form an annular seal.
 2. A method according to claim 1, wherein a plurality of tubular casing elements having external sealing elements disposed thereon are disposed in a wellbore, and wherein said workstring comprises a plurality of packer apparatuses each having an elastomeric packer element, the method further comprising: moving the workstring to a position in the wellbore at which said elastomeric packer elements are located at the same depths as said external sealing elements; and operating said electrically powered pump to actuate said plurality of packer apparatuses to deform the respective plurality of elastomeric packer elements outwardly to contact and deform a plurality of tubular casing elements outwardly and compress said plurality of external sealing elements against the surface of a wellbore or casing in which said tubular casing element is located to form a plurality of annular seals.
 3. A method according to claim 1, wherein the workstring further comprises sensor apparatus configured to sense characteristics of the formation of the portion of wellbore in which the workstring is located and/or to locate the position of external sealing elements of tubular casing elements disposed in the wellbore, the method further comprising: moving the workstring through the wellbore to a position at which the sensor apparatus indicates to an operator of the workstring that an annular seal is desirable at that location in the wellbore and/or an external sealing element is located adjacent said at least one elastomeric packer element; and operating said electrically powered pump to deform said elastomeric packer element outwardly to contact and deform said tubular casing element outwardly and compress said external sealing element against the surface of a wellbore or casing in which said tubular casing element is located to form an annular seal.
 4. A method according to claim 3, wherein the step of moving the workstring through the wellbore to a position at which the sensor apparatus indicates to an operator of the workstring that an annular seal is desirable at that location in the wellbore and/or an external sealing element is located adjacent said at least one elastomeric packer element includes operating fibre optic cables to sense wellbore parameters to indicate characteristics of the casing and/or fluid migration in the wellbore to the operator.
 5. A method according to claim 1, wherein said at least one packer apparatus comprises locking device configured to retain said elastomeric packer element in the outwardly deployed condition, said at least one packer apparatus further comprising a detachable portion containing said elastomeric packer element, the method further comprising: after said at least one packer apparatus has been operated to form an annular seal in the wellbore, detaching said detachable portion of said at least one packer apparatus of which the locking device has retained the elastomeric packer element in the outwardly deployed condition to deform casing to leave said detachable portion in the wellbore to act as a bridge plug.
 6. A method according to claim 5, further comprising pumping cement into the wellbore to sit on top of said detachable portion.
 7. A method according to claim 1, further comprising: lining a wellbore with a plurality of tubular casing elements; pumping cement into the annulus between said plurality of tubular casing elements and the surface of the wellbore or casing in which said plurality of casing elements is located; and locating said work string in the wellbore and operating said work string to form at least one annular seal in said wellbore before said cement has set.
 8. A workstring apparatus for creating an annular seal in the annulus between a wellbore and a casing disposed in the wellbore, the workstring comprising: at least one packer apparatus comprising: a first body portion removably connectable to a second body portion; an elastomeric packer element disposed on said first body portion, said elastomeric packer element configured to be deformed into an outwardly deployed condition in response to actuation of at least one piston disposed on said second body portion; a locking device disposed on said first body portion to retain said elastomeric packer element in the outwardly deployed condition; wherein said first body portion can be disconnected from said second body portion after said elastomeric packer element is moved to the outwardly deployed condition to deform casing in a wellbore in which the assembly is disposed to enable retrieval of said second body portion from said wellbore; a fluid accumulator arranged to hold fluid for actuation said at least one hydraulic cylinder; an electrically powered pump arranged to pump fluid from said fluid accumulator to actuate said at least one hydraulic cylinder; and a wireline arranged to supply electrical power to said electrically powered pump and hold said workstring at a desired position in a wellbore; wherein operating said electrically powered pump to actuate said at least one hydraulic cylinder deforms said elastomeric packer element outwardly to contact and deform a tubular casing element in which said packer apparatus is located outwardly to form an annular seal.
 9. An apparatus according to claim 8, further comprising sensor apparatus configured to sense characteristics of the formation of the portion of wellbore in which the workstring is located and/or to locate the position of an external sealing element of tubular casing elements disposed in the wellbore.
 10. An apparatus according to claim 9, wherein said sensor apparatus comprises at least one fibre optic cable and control apparatus configured to sense characteristics of the formation of the portion of wellbore in which the workstring is located and/or to locate the position of an external sealing element of tubular casing elements disposed in the wellbore based on light signals from said at least one fibre optic cable.
 11. An apparatus according to claim 8, wherein said locking means comprises: a first plurality of teeth disposed on an outer surface of said first body portion; and a ratchet member having a second plurality of teeth disposed thereon for engagement with said first plurality of teeth; wherein said ratchet member is able to move in a first direction along said first body portion during deformation of said elastomeric packer element but is prevent from movement in a second direction, opposite to said first direction by engagement of said first and second pluralities of teeth.
 12. An apparatus according to claim 11, wherein said ratchet member comprises a split ring.
 13. An apparatus according to claim 11, wherein said locking device further comprises a ratchet retainer ring in engagement with said elastomeric packer element.
 14. An apparatus according to claim 8, further comprising an electrically operated release apparatus to enable disconnection of the first body portion from the second body portion.
 15. An apparatus according to claim 8, further comprising a floating piston in fluid communication with both: fluid held in the fluid accumulator; and fluid located in a wellbore in use; such that fluid held in the fluid accumulator is isolated from fluid located in the wellbore but is at an equal pressure to fluid located in the wellbore.
 16. An apparatus according to claim 8, further comprising a plurality of packer apparatuses.
 17. A method of placing a casing patch in a wellbore, the method comprising: mounting a tubular casing element having an external sealing element disposed thereon on a workstring according to claim 8; moving said work string to a location in the wellbore at which a casing patch is required; operating said work string to deform said tubular casing element to form an annular seal at the desired location of said casing patch and disconnect said tubular casing element from the work string; and moving the work string away from said tubular casing element forming said casing patch.
 18. A method of completing a wellbore, the method comprising: lining a wellbore with at least one tubular casing element, said at least one tubular casing element comprising an external sealing element disposed thereon; and creating an annular seal between a wellbore and a casing disposed in the wellbore according to the method of claim
 1. 19. A tubular casing element for a wellbore, the tubular casing element comprising an external sealing element disposed thereon, wherein the external sealing element is a tubular sleeve formed from two or more of the following materials: an elastomer; a composite material; an alloy; a metal; or polyterafluoroethylene. 